Portable wheelchairs are becoming an increasingly popular alternative over the standard rigid models for wheelchair riders. The portable wheelchairs generally have a frame which folds or collapses for easy transportation, enabling a user to conveniently travel between various locations, such as from home to work, school, restaurants, the theater or any other site of interest. Typically, the portable wheelchairs are light in weight for improved maneuverability and handling. The frame is often formed from a tubular material, such as a lightweight, high-strength aircraft-grade aluminum tubing, to reduce the overall chair weight while providing the necessary strength. In efforts to further reduce the weight of the chair, the number of components comprising the chair frame has also been reduced.
The portable wheelchairs available in the art typically include opposed side frame assemblies having upper and lower horizontally extending bars and a pair of cross braces pivoted for movement about the lower frame bars. The opposite ends of each of the cross braces are pivotably mounted to a horizontally extending seat frame rod. A flexible seat is suspended between the laterally spaced seat frame rods. When the wheelchair is deployed, the seat frame is supported on brackets carried by the upper bars of the opposed side frames. The seat frame is held by the brackets in a superimposed position above the side frame assemblies. The wheelchair frame is folded or collapsed for transport by pivoting the cross braces about the respective side frame bars, raising the seat frame and drawing the opposed side frame assemblies towards one another.
With one type of folding wheelchair, the support brackets have a shallow groove formed to receive the seat frame rod. The seat frame is supported by the bracket during use, with the frame rod held within the groove by the weight of the seat assembly. Once the user vacates the chair, the wheelchair is easily folded for transport or storage by lifting the frame rods from the grooved brackets and moving the side frame assemblies towards one another. During operation, the user's weight often tends to urge the seat frame assembly off of the support bracket. When traveling over bumps or rough terrain, for example, the seat frame assembly will be lifted slightly from the support brackets, partially folding or collapsing the wheelchair. Thus, under certain operating conditions the wheelchair produces a sense of instability, resulting in user discomfort.
Other available wheelchairs include brackets or other means formed for supporting and retaining the seat frame in a stable superimposed position above the side frame assemblies. U.S. Pat. No. 4,790,553 discloses a wheelchair in which a support or mounting block is provided for carrying the seat frame assembly. The mounting block is formed with a cylindrical recess having a circumference extending beyond 180 degrees to provide a detent for retaining the seat frame rod. When the wheelchair frame is deployed, the seat frame rod is held in place by the opposed edges bordering the recess. As the wheelchair is folded or opened, the space between the opposed edges is resiliently enlarged to allow passage of the seat frame rod without requiring the application of excessive force. The mounting block of the disclosed wheelchair is formed for retaining the seat frame assembly above the opposed side frames during operation and for conveniently releasing the seat frame when folding or collapsing the wheelchair.
The side frame assemblies, the seat frame and the cross braces of the portable wheelchairs available in the art cooperate to provide a collapsible frame which may be conveniently deployed. The cross braces are pivotably mounted at opposite ends to the side frame assemblies and the seat frame. During operation, the support blocks distribute forces applied during operation between the side frame assemblies, cross braces and the seat frame. The operational forces imparted on the wheelchair during use may induce structural fatigue of the support brackets, eventually resulting in part failure. As the bracket or mount wears, the seat frame will not be adequately supported in a superimposed position above the side frame assemblies. Moreover, the support brackets will no longer evenly distribute the forces of operation, placing other components of the wheelchair frame under stress and potentially damaging the wheelchair.
Providing a folding wheelchair frame having a pair of cross bracing members pivotably coupled to the side frame assemblies would eliminate the need for a seat frame assembly and the required support brackets or blocks. The operational forces would be evenly distributed between the side frame assemblies and the cross braces, with the seat being supported directly by the opposed side frame assemblies. Allowing the seat to rest directly on the opposed side frames would substantially increase the structural life of the frame by reducing the stresses exerted on the various components of the wheelchair.
With the wheelchairs known in the prior art, the seat is suspended by the seat frame, which is in turn supported by the side frame assembly via the support brackets. Eliminating the seat frame assembly enables the seat to be supported directly by the opposed side frames. The effective height of the seat is thereby lowered, providing a stable ride similar to that offered by a rigid-type wheelchair frame. The wheelchair is lighter in weight without the seat frame assembly. Moreover, reducing the number of components substantially decreases the costs of manufacture and maintenance.
When the folding wheelchairs of the prior art are collapsed, the seat frame rods are vertically raised relative to the upper side frame bars. The raised seat frame assembly makes the collapsed wheelchair somewhat cumbersome. Eliminating the seat frame assembly enhances the portability of the folded wheelchair by reducing the number of components which must be accommodated when the frame is collapsed.
Accordingly, a foldable frame for a wheelchair including opposed side frames assemblies and cross bracing members pivotably coupled to the side frame assemblies is highly desirable. A wheelchair frame in which at least one of the cross braces interengages with one of the side frame assemblies to secure the cross bracing members in a weight-supporting condition when the frame is deployed is similarly desirable. A portable wheelchair frame providing the stability of a rigid-type wheelchair is also desirable. A wheelchair frame which is lightweight, compact, and which may be efficiently manufactured would be particularly useful. A foldable frame for a wheelchair which may be conveniently collapsed and transported would also be useful.
A primary object of the present invention, therefore, is to provide a foldable frame for a wheelchair having a cross bracing assembly pivotably coupled to the side frame assemblies for movement of the side frame assemblies between a deployed position and a collapsed position.
A further object of the present invention is to provide a foldable frame for a wheelchair having a pair of cross bracing members, with at least one of the cross bracing members secured in a weight-supporting condition when the wheelchair is deployed.
Another object of the present invention is to provide a foldable frame for a wheelchair in which the cross braces and the side frame assemblies are pivotably coupled together when the wheelchair frame is deployed.
Yet another object of the present invention is to provide a foldable frame for a wheelchair which provides the stability of a rigid wheelchair frame.
An additional object of the present invention is to provide a foldable frame for a wheelchair which is lightweight.
A more general object of the present invention is to provide a foldable frame for a wheelchair which is compact, and which may be efficiently manufactured and maintained.
The foldable wheelchair frame of the present invention has other objects and features of advantage which will become apparent from and are set forth in more detail in the description of the Best Mode for Carrying Out the Invention and the accompanying drawings.